Species-Specific Topography of Corticosteroid Receptor Types in Rat and Hamster Brain

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Abstract
In vivo and in vitro autoradiography with radiolabeled corticosteroid analogs as well as immunocytochemistry with monoclonal antibodies raised against the rat liver glucocorticoid receptor were used to determine the presence and the topography of two corticosteroid receptor systems (type I and type II) in hamster and rat brains. In the rat, the in vivo autoradiograms clearly revealed the retention by the type I receptor of tracer amount of [3H]corticosterone, primarily in the CA1 and CA2 cell field, dentate gyrus and lateral septum. In the hamster, tracer doses of [3H]cortisol were retained not only in the CA1, CA2, dentate gyrus and lateral septum, but also at high level in the CA3 and CA4 areas. In both species, immunocytochemistry showed the widespread distribution of the type II receptor sites in areas such as the hippocampus, lateral septum, hypothalamus (particularly in the paraventricular nucleus), thalamus and cortex (these results were also reflected in the in vitro autoradiography). Strong cell nuclear glucocorticoid immunoreactivity (type II-IR) was observed in the CA1 and CA2 (as well as CA3 and CA4 in the hamster) pyramidal neurons. In the hippocampus of intact animals, type II-IR was seen in the neuronal cell nuclei. Adrenalectomy caused a depletion of the type II-IR signal from the cell nucleus, which returned 1 h following subcutaneous administration of RU 28362 to adrenalectomized animals. The present study thus shows a similar but not identical distribution of the type I and type II receptor systems for corticosteroids in the hamster and rat brains. In contrast to the rat, the CA3 and CA4 cell fields in the hamster hippocampus contain higher numbers of these receptors.